Switch to Bazelisk.

Author: SpencerC

.bazelversion

@@ -0,0 +1 @@
+6.4.0

.github/workflows/build.yml

@@ -19,10 +19,13 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
-      - name: Install bazel
-        run: tools/install_deps.sh
+      - name: Mount bazel cache
+        uses: actions/cache@v3
+        with:
+          path: "~/.cache/bazel"
+          key: bazel
 
       - name: Run tests
         run: tools/run_tests.sh

README.md

@@ -17,6 +17,12 @@ with [Bazel](https://bazel.build).
 Setup
 -----
 
+Make sure Bazel is installed on your system. See the [Bazel
+documentation](https://docs.bazel.build/versions/master/install.html) for
+platform-specific instructions. We recommend using [Bazelisk](
+https://bazel.build/install/bazelisk.html) to ensure you are using a supported
+version.
+
 To use the Dart rules, add the following to your `WORKSPACE` file to add the
 external repositories for the Dart toolchain: